Second Nature looks to proceed on two fronts. First, Edelman outlines his account of brain function, which he calls "Neural Darwinism", and seeks to explain how the brain consequently gives rise to consciousness. Second, he attempts to unravel the implications of this empirical theory for epistemology, the branch of philosophy which studies the nature of knowledge. The premise that our theory of knowledge must in some way depend upon our theory of mind is highly plausible and promising. It is a shame, therefore, that the project is not carried out with greater accuracy, care and engagement with the philosophical debate. I shall return to these criticisms later.

For now, we should observe that the project is carried out against the omnipresent backdrop of scientism. Thus, Edelman opens with the now familiar narrative of the inexorable march of the empirical sciences into the traditional territory of the humanities, most notable philosophy, highlighting as he goes their accompanying predictive and technological successes. The title of the book refers to the distinction between "nature" and "human nature", which has traditionally been construed as the distinction between the subject matter of the empirical sciences and the humanities respectively. A philosophical audience will likely be reminded of John McDowell's sophisticated discussion of 'first' and 'second nature', although Edelman makes no reference to this. In any case, Edelman is dismissive of any form of traditional a priori or "armchair" metaphysics, and sees no reason why science cannot penetrate into every area of human inquiry. This includes both "nature" and "human nature". Some philosophers have thought otherwise with respect to the mind, and consequently with respect to epistemology. This, Edelman claims, is due to the pernicious influence of Cartesian dualism (the claim that mind and body are separate substances).

Edelman has high hopes for a scientific theory of consciousness. It would, he claims, dispel dualism, lumped in with "panpsychism, mysterianism and spooky forces" (9), as well as corroborating the view that the human mind is the product of natural selection -- although he offers no explanation of why an artifact of natural selection must, in principle, be fully explicable by the methods of the natural sciences. He also suggests early on that we can hope to reduce the study of creativity, ethics and aesthetics to "hard science" (p. 10). On this point, however, Edelman's confidence appears to wane as he later tells us that "a fully reductive scientific explanation of … ethics and aesthetics is not desirable, likely, or forthcoming" (66). Be this as it may, Edelman's primary concern is with what he calls "brain-based epistemology"; the claim being that a theory of knowledge should be, and now can be, grounded in a scientific account of the workings of the physical brain. This position, he argues, is an extension of W. V. Quine's naturalized epistemology. Quine famously argued that the central task of epistemology is to understand the causal relations between the evidence of experience and our knowledge of the world, provisionally leaving aside normative considerations. Edelman proposes that we should employ neuroscience in order to delve deeper into the brain as the seat of consciousness. The reasonable thought is that if we want to understand the conditions in which the brain is a state of knowledge, then we had better start with an account of how the brain actually works.

Briefly, neural Darwinism maintains that the brain is a selectional system. There is variation in the development of neuronal circuits, and selective pressure in the face of behavior and experience, resulting in the strengthening or weakening of particular synapses which become fixed with time. This is achieved by the mechanism of "reentry", which is essentially the signaling from one brain region or module to another. The more frequently these signal paths are employed, the stronger they become. As the signal paths in the brain are interconnected, strong pathways exert lateral pressure on other regions of the brain, bringing our neural functioning into balance (Edelman employs the helpful metaphor of a string quartet tied together with fine thread). By contrast, unused, or little used, pathways atrophy and eventually die. The brain contains something like 100 billion nerve cells, with 100 trillion connections, so, needless to say, the details of the process are extraordinarily complicated.

The philosophical claims come thick and fast on the basis of this model, and it is sad to say that they are rarely adequately defended, and sometimes plain incoherent. Consider page 41 alone. Philosophers are alleged to ask fundamentally confused questions the ontological status of qualia. They ask whether or not the "feels" of mental states, such as the tang of a lemon or the smell of a rose, actually exist. But qualia, Edelman claims, are processes. Presumably the suppressed premise is that one cannot legitimately ask whether processes exist. Bizarrely, Edelman also attributes to philosophers the mistaken belief that perception is wholly independent of mind and language. But how could anyone think that perception is independent of the mind? He also takes philosophers to task for thinking that the continuity of some system or substance implies that it has an essence, and that all structures and properties have functions (haven't philosophers considered dreams? Edelman asks).

All this is depressingly blasé and inaccurate. Edelman apparently thinks that he can correct two millennia of philosophy on the basis of a contentious empirical theory and a passing acquaintance with the discipline -- he is unashamed to admit, for example, that his taxonomy of epistemology comes from glancing through the index of a textbook (44). The problem is evident. On the one hand, Edelman's scientism makes him contemptuous of philosophical enterprise. On the other hand, Edelman is attempting to press a series of philosophical theses. The result is a lack of serious engagement with the philosophical subject matter he is discussing. I began by observing that the book has two main objectives. There is plenty to recommend in Edelman's lively and engaging presentation of neural Darwinism, but his foray into philosophy is a failure and readers should look elsewhere.

Michael-John Turp has an MA in philosophy from Durham University and is currently pursuing doctoral research into philosophical naturalism and normativity, also at Durham University. His research interests include metaphilosophy, philosophy of science, epistemology, ethics and moral psychology.

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